1. Field
Disclosed herein is an inductive component having at least one coil and a soft magnetic core made from a ferromagnetic material. Also disclosed are methods for producing inductive components in particular, which have a soft magnetic core that consists of a powder composite.
2. Description of Related Art
Soft magnetic powder composites as pressed magnetic cores have been known for a long time.
Firstly, pressed powder composites made from iron powder are known. A permeability area of approximately 10 to 300 can be covered quite well using this magnetic core. The saturation flux density, which can be obtained using these magnetic cores, is at approximately 1.6 tesla. The application frequencies are generally below 50 kHz due to the size of the comparatively low resistivity and the iron particles.
Pressed powder composites made from soft magnetic crystalline iron aluminum silicon alloys are known as well. Application frequencies exceeding 100 kHz can be reached with these composites due to the comparatively higher resistivity.
Saturation flux densities and permabilities, which are particularly good, can be achieved using powder composite materials, which are based on crystalline mumetals. Permeabilities reaching up to 500 can be achieved via an exact allocation of the nickel content allowing for application frequencies exceeding 100 kHz due to the comparatively minor remagnetizing losses.
However, these three known powder composites can only be processed into very simple geometric forms, as the available press technologies only allow for a limited range. In particular, only toroids and/or pot cores can be produced.
To avoid this disadvantage, an injection molding method was presented in DE 198 46 781 A1, in which nano-crystalline alloys are incorporated into an injection molding capable plastic, and subsequently processed into soft magnetic cores by means of an injection molding method.
It became apparent, however, that the injection molding approaches, which initially seemed to be quite promising, had limitations. A major disadvantage consisted in the alloy particles of the alloy powder made from amorphous or nano-crystalline alloys being exposed to extreme mechanical loads particularly while being injected into the deployed tools. This generally led to damages of the alloy particles' surface insulation. The alloy particles' damaged surface insulations in turn leads to increased remagnetizing losses due to bulky eddy currents in the produced soft magnetic cores.
An additional problem concerning the injection molding method consists in the constancy of the coils' insulation with respect to the soft magnetic core. The mold, which is equipped with coils during the production process, acts rather like an abrasive due to the presence of alloy particles, which are integrated therein, which leads to increased damages of the coils' insulation. Increased serious damage occurs in particular, when using coils consisting of copper wires that are insulated with lacquer, or copper strands that are insulated with lacquer.
Furthermore, the need for very expensive injection molding molds, the production of which is very costly, is a disadvantage of the injection molding method.